1 /*
2 * Diffie-Hellman-Merkle key exchange (server side)
3 *
4 * Copyright The Mbed TLS Contributors
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 */
19
20 #include "mbedtls/build_info.h"
21
22 #if defined(MBEDTLS_PLATFORM_C)
23 #include "mbedtls/platform.h"
24 #else
25 #include <stdio.h>
26 #include <stdlib.h>
27 #define mbedtls_printf printf
28 #define mbedtls_time_t time_t
29 #define mbedtls_exit exit
30 #define MBEDTLS_EXIT_SUCCESS EXIT_SUCCESS
31 #define MBEDTLS_EXIT_FAILURE EXIT_FAILURE
32 #endif /* MBEDTLS_PLATFORM_C */
33
34 #if defined(MBEDTLS_AES_C) && defined(MBEDTLS_DHM_C) && \
35 defined(MBEDTLS_ENTROPY_C) && defined(MBEDTLS_NET_C) && \
36 defined(MBEDTLS_RSA_C) && defined(MBEDTLS_SHA256_C) && \
37 defined(MBEDTLS_FS_IO) && defined(MBEDTLS_CTR_DRBG_C) && \
38 defined(MBEDTLS_SHA1_C)
39 #include "mbedtls/net_sockets.h"
40 #include "mbedtls/aes.h"
41 #include "mbedtls/dhm.h"
42 #include "mbedtls/rsa.h"
43 #include "mbedtls/sha1.h"
44 #include "mbedtls/entropy.h"
45 #include "mbedtls/ctr_drbg.h"
46
47 #include <stdio.h>
48 #include <string.h>
49 #endif
50
51 #define SERVER_PORT "11999"
52 #define PLAINTEXT "==Hello there!=="
53
54 #if !defined(MBEDTLS_AES_C) || !defined(MBEDTLS_DHM_C) || \
55 !defined(MBEDTLS_ENTROPY_C) || !defined(MBEDTLS_NET_C) || \
56 !defined(MBEDTLS_RSA_C) || !defined(MBEDTLS_SHA256_C) || \
57 !defined(MBEDTLS_FS_IO) || !defined(MBEDTLS_CTR_DRBG_C) || \
58 !defined(MBEDTLS_SHA1_C)
main(void)59 int main( void )
60 {
61 mbedtls_printf("MBEDTLS_AES_C and/or MBEDTLS_DHM_C and/or MBEDTLS_ENTROPY_C "
62 "and/or MBEDTLS_NET_C and/or MBEDTLS_RSA_C and/or "
63 "MBEDTLS_SHA256_C and/or MBEDTLS_FS_IO and/or "
64 "MBEDTLS_CTR_DRBG_C not defined.\n");
65 mbedtls_exit( 0 );
66 }
67 #else
68
69
main(void)70 int main( void )
71 {
72 FILE *f;
73
74 int ret = 1;
75 int exit_code = MBEDTLS_EXIT_FAILURE;
76 size_t n, buflen;
77 mbedtls_net_context listen_fd, client_fd;
78
79 unsigned char buf[2048];
80 unsigned char hash[32];
81 unsigned char buf2[2];
82 const char *pers = "dh_server";
83
84 mbedtls_entropy_context entropy;
85 mbedtls_ctr_drbg_context ctr_drbg;
86 mbedtls_rsa_context rsa;
87 mbedtls_dhm_context dhm;
88 mbedtls_aes_context aes;
89
90 mbedtls_mpi N, P, Q, D, E;
91
92 mbedtls_net_init( &listen_fd );
93 mbedtls_net_init( &client_fd );
94 mbedtls_dhm_init( &dhm );
95 mbedtls_aes_init( &aes );
96 mbedtls_ctr_drbg_init( &ctr_drbg );
97
98 mbedtls_mpi_init( &N ); mbedtls_mpi_init( &P ); mbedtls_mpi_init( &Q );
99 mbedtls_mpi_init( &D ); mbedtls_mpi_init( &E );
100
101 /*
102 * 1. Setup the RNG
103 */
104 mbedtls_printf( "\n . Seeding the random number generator" );
105 fflush( stdout );
106
107 mbedtls_entropy_init( &entropy );
108 if( ( ret = mbedtls_ctr_drbg_seed( &ctr_drbg, mbedtls_entropy_func, &entropy,
109 (const unsigned char *) pers,
110 strlen( pers ) ) ) != 0 )
111 {
112 mbedtls_printf( " failed\n ! mbedtls_ctr_drbg_seed returned %d\n", ret );
113 goto exit;
114 }
115
116 /*
117 * 2a. Read the server's private RSA key
118 */
119 mbedtls_printf( "\n . Reading private key from rsa_priv.txt" );
120 fflush( stdout );
121
122 if( ( f = fopen( "rsa_priv.txt", "rb" ) ) == NULL )
123 {
124 mbedtls_printf( " failed\n ! Could not open rsa_priv.txt\n" \
125 " ! Please run rsa_genkey first\n\n" );
126 goto exit;
127 }
128
129 mbedtls_rsa_init( &rsa );
130
131 if( ( ret = mbedtls_mpi_read_file( &N , 16, f ) ) != 0 ||
132 ( ret = mbedtls_mpi_read_file( &E , 16, f ) ) != 0 ||
133 ( ret = mbedtls_mpi_read_file( &D , 16, f ) ) != 0 ||
134 ( ret = mbedtls_mpi_read_file( &P , 16, f ) ) != 0 ||
135 ( ret = mbedtls_mpi_read_file( &Q , 16, f ) ) != 0 )
136 {
137 mbedtls_printf( " failed\n ! mbedtls_mpi_read_file returned %d\n\n",
138 ret );
139 fclose( f );
140 goto exit;
141 }
142 fclose( f );
143
144 if( ( ret = mbedtls_rsa_import( &rsa, &N, &P, &Q, &D, &E ) ) != 0 )
145 {
146 mbedtls_printf( " failed\n ! mbedtls_rsa_import returned %d\n\n",
147 ret );
148 goto exit;
149 }
150
151 if( ( ret = mbedtls_rsa_complete( &rsa ) ) != 0 )
152 {
153 mbedtls_printf( " failed\n ! mbedtls_rsa_complete returned %d\n\n",
154 ret );
155 goto exit;
156 }
157
158 /*
159 * 2b. Get the DHM modulus and generator
160 */
161 mbedtls_printf( "\n . Reading DH parameters from dh_prime.txt" );
162 fflush( stdout );
163
164 if( ( f = fopen( "dh_prime.txt", "rb" ) ) == NULL )
165 {
166 mbedtls_printf( " failed\n ! Could not open dh_prime.txt\n" \
167 " ! Please run dh_genprime first\n\n" );
168 goto exit;
169 }
170
171 if( mbedtls_mpi_read_file( &dhm.MBEDTLS_PRIVATE(P), 16, f ) != 0 ||
172 mbedtls_mpi_read_file( &dhm.MBEDTLS_PRIVATE(G), 16, f ) != 0 )
173 {
174 mbedtls_printf( " failed\n ! Invalid DH parameter file\n\n" );
175 fclose( f );
176 goto exit;
177 }
178
179 fclose( f );
180
181 /*
182 * 3. Wait for a client to connect
183 */
184 mbedtls_printf( "\n . Waiting for a remote connection" );
185 fflush( stdout );
186
187 if( ( ret = mbedtls_net_bind( &listen_fd, NULL, SERVER_PORT, MBEDTLS_NET_PROTO_TCP ) ) != 0 )
188 {
189 mbedtls_printf( " failed\n ! mbedtls_net_bind returned %d\n\n", ret );
190 goto exit;
191 }
192
193 if( ( ret = mbedtls_net_accept( &listen_fd, &client_fd,
194 NULL, 0, NULL ) ) != 0 )
195 {
196 mbedtls_printf( " failed\n ! mbedtls_net_accept returned %d\n\n", ret );
197 goto exit;
198 }
199
200 /*
201 * 4. Setup the DH parameters (P,G,Ys)
202 */
203 mbedtls_printf( "\n . Sending the server's DH parameters" );
204 fflush( stdout );
205
206 memset( buf, 0, sizeof( buf ) );
207
208 if( ( ret = mbedtls_dhm_make_params( &dhm, (int) mbedtls_mpi_size( &dhm.MBEDTLS_PRIVATE(P) ), buf, &n,
209 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
210 {
211 mbedtls_printf( " failed\n ! mbedtls_dhm_make_params returned %d\n\n", ret );
212 goto exit;
213 }
214
215 /*
216 * 5. Sign the parameters and send them
217 */
218 if( ( ret = mbedtls_sha1( buf, n, hash ) ) != 0 )
219 {
220 mbedtls_printf( " failed\n ! mbedtls_sha1 returned %d\n\n", ret );
221 goto exit;
222 }
223
224 buf[n ] = (unsigned char)( rsa.MBEDTLS_PRIVATE(len) >> 8 );
225 buf[n + 1] = (unsigned char)( rsa.MBEDTLS_PRIVATE(len) );
226
227 if( ( ret = mbedtls_rsa_pkcs1_sign( &rsa, NULL, NULL, MBEDTLS_MD_SHA256,
228 32, hash, buf + n + 2 ) ) != 0 )
229 {
230 mbedtls_printf( " failed\n ! mbedtls_rsa_pkcs1_sign returned %d\n\n", ret );
231 goto exit;
232 }
233
234 buflen = n + 2 + rsa.MBEDTLS_PRIVATE(len);
235 buf2[0] = (unsigned char)( buflen >> 8 );
236 buf2[1] = (unsigned char)( buflen );
237
238 if( ( ret = mbedtls_net_send( &client_fd, buf2, 2 ) ) != 2 ||
239 ( ret = mbedtls_net_send( &client_fd, buf, buflen ) ) != (int) buflen )
240 {
241 mbedtls_printf( " failed\n ! mbedtls_net_send returned %d\n\n", ret );
242 goto exit;
243 }
244
245 /*
246 * 6. Get the client's public value: Yc = G ^ Xc mod P
247 */
248 mbedtls_printf( "\n . Receiving the client's public value" );
249 fflush( stdout );
250
251 memset( buf, 0, sizeof( buf ) );
252
253 n = mbedtls_dhm_get_len( &dhm );
254 if( ( ret = mbedtls_net_recv( &client_fd, buf, n ) ) != (int) n )
255 {
256 mbedtls_printf( " failed\n ! mbedtls_net_recv returned %d\n\n", ret );
257 goto exit;
258 }
259
260 if( ( ret = mbedtls_dhm_read_public( &dhm, buf, n ) ) != 0 )
261 {
262 mbedtls_printf( " failed\n ! mbedtls_dhm_read_public returned %d\n\n", ret );
263 goto exit;
264 }
265
266 /*
267 * 7. Derive the shared secret: K = Ys ^ Xc mod P
268 */
269 mbedtls_printf( "\n . Shared secret: " );
270 fflush( stdout );
271
272 if( ( ret = mbedtls_dhm_calc_secret( &dhm, buf, sizeof( buf ), &n,
273 mbedtls_ctr_drbg_random, &ctr_drbg ) ) != 0 )
274 {
275 mbedtls_printf( " failed\n ! mbedtls_dhm_calc_secret returned %d\n\n", ret );
276 goto exit;
277 }
278
279 for( n = 0; n < 16; n++ )
280 mbedtls_printf( "%02x", buf[n] );
281
282 /*
283 * 8. Setup the AES-256 encryption key
284 *
285 * This is an overly simplified example; best practice is
286 * to hash the shared secret with a random value to derive
287 * the keying material for the encryption/decryption keys
288 * and MACs.
289 */
290 mbedtls_printf( "...\n . Encrypting and sending the ciphertext" );
291 fflush( stdout );
292
293 ret = mbedtls_aes_setkey_enc( &aes, buf, 256 );
294 if( ret != 0 )
295 goto exit;
296 memcpy( buf, PLAINTEXT, 16 );
297 ret = mbedtls_aes_crypt_ecb( &aes, MBEDTLS_AES_ENCRYPT, buf, buf );
298 if( ret != 0 )
299 goto exit;
300
301 if( ( ret = mbedtls_net_send( &client_fd, buf, 16 ) ) != 16 )
302 {
303 mbedtls_printf( " failed\n ! mbedtls_net_send returned %d\n\n", ret );
304 goto exit;
305 }
306
307 mbedtls_printf( "\n\n" );
308
309 exit_code = MBEDTLS_EXIT_SUCCESS;
310
311 exit:
312
313 mbedtls_mpi_free( &N ); mbedtls_mpi_free( &P ); mbedtls_mpi_free( &Q );
314 mbedtls_mpi_free( &D ); mbedtls_mpi_free( &E );
315
316 mbedtls_net_free( &client_fd );
317 mbedtls_net_free( &listen_fd );
318
319 mbedtls_aes_free( &aes );
320 mbedtls_rsa_free( &rsa );
321 mbedtls_dhm_free( &dhm );
322 mbedtls_ctr_drbg_free( &ctr_drbg );
323 mbedtls_entropy_free( &entropy );
324
325 #if defined(_WIN32)
326 mbedtls_printf( " + Press Enter to exit this program.\n" );
327 fflush( stdout ); getchar();
328 #endif
329
330 mbedtls_exit( exit_code );
331 }
332 #endif /* MBEDTLS_AES_C && MBEDTLS_DHM_C && MBEDTLS_ENTROPY_C &&
333 MBEDTLS_NET_C && MBEDTLS_RSA_C && MBEDTLS_SHA256_C &&
334 MBEDTLS_FS_IO && MBEDTLS_CTR_DRBG_C */
335